Pierce nut applying method

ABSTRACT

A method for rapidly attaching pierce nuts to a sheet which does not require completely new tooling for different designs of sheets. The nuts are made from a strip of metal and are complete except that they are left attached to one another and are thus predictably oriented. They are supplied to the attaching mechanism in rolled strip form. The attaching mechanism is a standardized unit enclosed in a single housing which automatically locates the end nut of the strip over the workpiece sheet, severs the nut from the strip, pierces the sheet with the nut and clinches the nut to the sheet while, if desired, embossing the sheet at the opening made therein by the nut. As many such standarized nut attaching units may be used simultaneously in a single punch press as are required, the tooling to be used comprising mainly means for locating the units relative to the sheet in the punch press.

United States Patent Grube Apr. 15, 1975 [54] PIERCE NUT APPLYING METHOD3,229,363 l/l966 Bien 29/432 [75] Inventor. William L. Grube, LakeBluff, Ill. Primary Examinerwcharlie T Moon [73] Assignee: MacLean-FoggLock Nut C0.,

Mundelein, Ill. [57] ABSTRACT 22 Filed; 23, 1973 A method for rapidlyattaching pierce nuts to a sheet which does not require completely newtooling for dif- [21] Appl' 335,235 ferent designs of sheets. The nutsare made from a R l t d U s A li ti D t strip of metal and are completeexcept that they are [62] Division of 83 408 Oct 23 1970 left attachedto one another and are thus predictably abandoned oriented. They aresupplied to the attaching mechanism in rolled strip form. The attachingmechanism is 52 US. Cl. 29/417; 29/4322; 29/509; a Standardized enclosedin a Sihgh3 housing which 29/241353; 151/4112; 151/4173 automaticallylocates the end nut of the strip over the 51 Int. Cl B23p 17/00; 1323p11/00 workpiece sheet, Severs the hut from the Strip, pierces 5 Field ofSearch 29/417 432 4321 4322 the sheet with the nut and clinches the nutto the sheet 29/509, 24353; 221/73; 151/4172 4173 while, if desired,embossing the sheet at the opening made therein by the nut. As many suchstandarized [56] References Cited nut attaching units may be usedsimultaneously in a UNITED STATES PATENTS single punch press as arerequired, the tooling to be used comprising mainly means for locatingthe units iifi to 3,140,010 7/1964 Double 221/73 4 Claims, 16 DrawingFigures PATENTEDAPR 1 sum SHEU20F 3 PIERCE NUT APPLYING METHOD This is adivision of my copending application Ser. No. 83,408 tiled Oct. 23,1970,now abandoned.

This invention relates to a method of attaching pierce nuts to a sheet.It is particularly adapted for use with pierce nuts in strip form madein accordance with the article and method disclosed and claimed in mycopending application Ser. No. 21,777, filed Mar. 28, 1970, now Us. Pat.No. 3,704,507.

. It has been known for many years to secure a nut to a sheet over ahole therein so that the sheet could be secured to aframe or anothersheet by a screw without requiring the assembler to hold the screw overthe opening on one side of the sheet while the machine screw fastenerwas inserted from the other side. It has also been known to use a nut asa punch to pierce an opening in a sheet, and to deform either the sheet,or the nut, or both to clinch the nut in place on the sheet in theopening, thus at once forming the opening, locating the nut properlyover the opening and securing the nut non-rotatively to the sheet. Suchnuts are known as pierce or clinch nuts.

' It may be appreciated that the use of pierce nuts is limited toextremely high volume applications since a considerable amount oftooling and set-up is required in the handling, selecting and feeding ofindividual nuts. Once designed, the tooling can be used only for thespecific application for which it was designed, i.e., each design isgood only for one application, and if any changes are made in the sheetor location and number of nuts, completelynew tooling is required.

The most difficult area in the use of pierce nuts has been in thehandling of the individual nuts. These must be selected from a hopper,oriented and fed individually to the properlocation on the sheet towhich they are to be applied. Present selecting and feeding mechanismare limited as to the rate at which the pierce nuts can be handled.

It is an object of this invention to provide a method of feeding andapplying pierce nuts to a workpiece sheet which method is faster,simpler and less expensive than methods now available.

Another object of this invention is to provide a method of feeding andapplying pierce nuts to a sheet which is unitized and standarized andtherefore more flexible in its applciations, such that expensivecustomdesigned tooling can be substantially eliminated.

. These and other objects of this invention will become apparent fromthe following detailed description of a preferred embodiment of theinvention whentaken together with the accompanying drawings in which:

FIG. 1 is a section through the pierce nut, workpiece and clinching dieof the type to which this invention may be applied;

FIG. 2 is a plan view of the bottom die of FIG. 1;

FIG. 3 is an elevation in section of the bottom die of FIG. 2 takenalong line 3-3 thereof;

FIG. 4 is a side elevational view of a known punch press in which thisinvention is installed;

FIG. 5 is an enlarged longitudinal section through a strip of nuts ofthe kind used with this invention;

FIGS. 6 and 7 are plan and side views, respectively, on a reduced scaleof the strip of FIG. 5;

FIGS. 6 and 7 are plan and sideviews, respectively, on a reduced scaleof the strip of FIG. 5;

FIGS. 8 and 9 are sections through the strip of FIG. 5 taken along lines88 and 99, respectively, of FIG. 7;

FIGS. 10 and 11 are, respectively, front and side elevations of thedevice of this invention, FIG. 10 being a section taken along line 10l0of FIG. 11;

FIG. 12 is a bottom view of the device of this invention taken alongline l2l2 of FIG. 10;

FIG. 13 is a plan view in section through the device of FIG. 10 takenalong line 13-13 thereof;

FIG. 14 is a side elevational view in section of the device of FIG. 10taken along line 14-14 of FIG. 10;

FIG. 15 is a front elevational view in section of the device similar toFIG. 10, but showing the device in another stage of operation; and

FIG. 16 is an enlarged vertical section through the shear insert of thetool.

The present invention is based upon the use of pierce nuts in strip formsuch as are described and claimed in my aforesaid copending applicationSer. No. 21,777 filed Mar. 28, 1970, now US. Pat. No. 3,704,507. Asthere described, the nuts are formed in a strip of metal having rolledtherein the requisite laterally extending flanges for pierce nuts,complete with properly threaded holes and with perforated connectorsjoining adjacent nuts together to preserve the original orientation andplanar relation of the nuts to one another. The use of these stripnuts", as they shall be referred to hereinafter, eliminates at once thevibration feedhoppers and their chutes or other devices normally used toselect, orient and conduct the nuts to the point of application on theworkpiece. It also eliminates dependence upon the limitations in therate of selection and feed of the nuts imposed by such hoppers andchutes, as well as the time lost in correcting malfunctions thereof.

The strip nuts are inserted into a unit incorporating this invention,which unit has been affixed to the punch press in which the fastening ofthe nut to the workpiece is to be effected. Said unit is provided withmeans for converting the vertical reciprocating motion of the ram of thepress into horizontal reciprocatory motion utilized to advance thestrip, one nut at a time, to the punch which then severs the nut fromthe strip, pierces the workpiece with the severed nut and clinches thenut to the workpiece. Thus the feeding, severing, piercing and clinchingoperations are all performed by the said unit, utilizing the verticalmotion and energy of the punch to power all of such operations. Severalsuch units may be affixed to the same punch press to attachsimultaneously a plurality of clinch nuts to a workpiece.

Referring now to the drawings for a detailed description of theinvention, attention is directed first to FIGS. l3 which illustrate thepreferred form of nut and clinching method to be used with thisinvention, although it is understood that other forms of nuts andclinching methods can also be used. In FIG. 1, the nut is shown at 20 inthe position it assumes with respect to a workpiece 21 which is shown inthe form of a sheet metal panel, the nut having pierced an opening 22 inthe workpiece and left a slug 23 which is to be ejected by succeedingslugs through an opening 24 in the bottom die 25. The piercing operationis effected by a punch 31 reciprocating in an opening 30 in a pad 26. Inthe form selected to illustrate this invention, said bottom die 25, incooperation with pad 26, also forms a boss 27 in workpiece 21 so thatthe surface 28 of nut 20 will be co-planar, or flush, with surface 29 ofworkpiece 21 to make it possible for the workpiece to be secured toanother surface of the structure of which workpiece 21 is a part.

FIG. 2 shows the bottom die 25 in plan view and also shows, forclarification, the inwardly projecting means at the corners 32 fordeforming the corners of the nut 20 to effect the desired interlock withworkpiece 21. FIG. 3 shows a section through the corners 32 of bottomdie 25 and the location, in dotted outline, of the workpiece 21 andflanged nut 20 at the beginning of the piercing operation.

The nuts as supplied to die 25 are shown in FIGS. -9. The individualnuts (FIG. 8 and 9) are substantially square in cross section and areformed with laterally and oppositely extending flanges 33, 34 whichserve as abutments to limit the movement of a nut into a workpiece ithas pierced. The portion 19 of nut extending beyond flanges 33,34 issometimes termed the pilot or shank portion of the nut and is theportion which is used as a punch to pierce an opening in workpiece 21.Said workpiece may be a sheet metal panel, bracket or machine part. Thenuts are supplied in strip form, each nut being connected to itsadjacent nut by portions 35, 36 of the flanges 33, 34 which remain whenopenings 37 are punched in the flanged strip of stock to form theindividual nuts. The details of the strip form of nut and the method ofmaking and applying it to a workpiece are described and claimed in myaforesaid US. Pat. No. 3,704,507.

The nuts in the stip forms of FIGS. 6 and 7 are furnished in coils 38,as shown in FIG. 4, to a punch press 39 in which the nut applicationtool 40 of this invention is installed. The strip is fed to tool 40 withthe flanges 35, 36 uppermost as shown in FIG. 5. If more than one nut isto be applied to a workpiece at a time, then as many application tools40 and coils 38 are provided in punch press 39 as there are nuts to besimultaneously applied. Appropriate fixtures (not shown) will beprovided to locate the workpiece in press 39 relative to the tools 40.

It has been found that although, ideally, the connecting portions 35, 36should be punched out in the tool 40 to leave a neat and symmetrical nut20, in practice these connecting portions are not generally visible tothe exterior of the panel so that appearance is a minor factor. Inaddition, the slugs formed by the punched out connecting portions 35, 36create a disposal problem which, if not properly solved, might result inhaving the slugs fall upon and get pressed into the workpiece to mar itsappearance. In the form illustrated, therefore, the connecting portionsare sheared in half so that each nut has one-half of a connectingportions 35, 36 extending from opposite sides thereof.

Tool 40 is shown in FIGS. l0l5. It is comprised of a verticallyreciprocable plunger 41 and an assembly carried by said plunger andadapted to be suspended over bottom die 25 in a die block 42 secured tothe bed (not shown) of punch press 39. The workpiece 21 is showndisposed between die 25 and the bottom of the tool assembly, and thenuts in strip form from coil 38 are shown at 43.

Referring to the cross sectional view of the tool shown in FIG. 15, thepunch 31 is secured to a mounting plate 44 which, in turn, is adapted tobe secured to the reciprocating ram (not shown) of punch press 39.Plunger 41 is comprised of a punch retainer 45 which is centered inmounting plate 44 and which, in turn, centers the upper portion 46 ofpunch 31. A fastener 47 secures plate 44, puch 31 and retainer 45together to function as a unit.

The bottom end of retainer 45 has a radially outwardly extending flange48 and reciprocates in a recess 49 in a housing 50 which is splitvertically in the plane of FIG. 15 into two substantially symmetricalparts 51 and 52 (FIG. 11). The parts 51 and 52 are secured together byappropriate screws 53 (FIG. 13). A compression spring 54 bears againstthe bottom of recess 49 and urges retainer 45 upward. A stop is providedfor retainer 45 by a washer 55 on housing 50 extending over recess 49and adapted to be engaged by flange 48.

Across the bottom of housing 50 is secured a feed block 56 which isformed with a T-shaped groove 57 in the upper part thereof and to theright of punch 31 as viewed in FIG. 15 along which the strip nuts 43 arefed to the punch. The strip nuts are retained in the groove by thebottom 58 of the housing 50. A finger spring 59 is secured to thesloping bottom of a centrally disposed groove 60 in feed block 56, saidspring extending into groove 57 and into the space between adjacent nuts20 in the strip nuts 43. Spring 59 allows the strip nuts to be fedtoward punch 31, but prevents movement of the nuts in the oppositedirection.

Adjacent punch 31, feed block 56 is provided with a shear insert 61(FIG. 16) which extends under the connecting flange parts 35 and 36between adjacent nuts 20 and cooperates with punch 31 to shear saidparts 35 and 36 in half. This leaves one-half of each connecting partwith the nut 20 so that each nut has portions of the connecting partsextending from opposite sides thereof to present a symmetricalappearance. Next to shear insert 61 in feed block 56 is an opening 62through which the severed nut is pushed to the workpiece by punch 31 forthe piercing, embossing and clinching operations.

Slots 63 are formed in feed block 56 adjacent opening 62 in which theconnecting parts 35, 36 extending from the severed nut 20 are receivedand slide vertically. An embossing plate 64 is secured to the bottom offeed block 56 to cooperate with bottom die 25 during the embossingoperation.

Strip nuts 43 are advanced intermittently toward punch 31 by a pawl 65which is bifurcated at its right hand end as viewed in FIGS. 10 and 15to receive pivotally one end ofa rocker arm 66, the other end of whichis pivoted at 67 to a pivot block 68 horizontally adjustable in a recess69 in housing 50. The nose 70 of pawl 65 is adapted to enter the opening37 between adjacent nuts and is urged to enter said openings by atension spring 71 connecting a tail portion 72 on pawl 65 and anelevated point on housing 50.

Referring now to FIG. 10, horizontal reciprocating movement is impartedto pawl 65 by a drive link 73 connected at one end to a pivot pin 74passing through rocker arm 66 and movable therewith, and connected atits other end to a pin 75 which is also the shaft about which a roller76 rotates. Said other end reciprocates in a recess 77 in housing 50,and the reciprocating movement is transmitted to rocker arm 66 and thenthrough said rocker arm 66, at an amplified rate, to pawl 65 through apin 78 connecting the arm to the pawl. Drive link 73 receives itsreciprocating movement from a cam surface 79 (FIG. 15) in a slot on oneside of punch 31 on which roller 76 rolls. The return reciprocatingmovement is derived from a cam surface 80 in a slot on the other side ofpunch 31 in which a pin 81 rides, said pin having one end connected todrive link 73.

It may be apparent from the foregoing description of drive link 73,roller 76 and pin 83 that as punch 31 moves downward, it first causesroller 76 and drive link 73 to move to the left as viewed in FIGS and15, which then causes pawl 65, then received in an opening betweenadjacentnuts in the strip nuts 43, to push said strip nuts to the leftas viewed in FIGS. 10 and until the end nut of the strip is directlyover opening 62. At the time said end nut is so located, roller 76 isout of contact with cam surface 79 and thereafter rides on the verticalsurface 83 on the side of punch 31 which acts as a dwell surface whilethe punch continues its downward stroke. On the return or upward stroke,pin 81 engages cam surface 80 and causes a reverse movement of drivelink 73. On such reverse movement pawl 65 will be moved out of theopening in the strip nuts it then occupied and will slide over one nutand drop into the next opening in readiness to advance the end nut againunder punch 31. Spring finger 59 holds the strip nuts against backwardmovement with pawl 65.

The point at which the pawl 65 ceases to drive the strip nuts 43 towardpunch 31 is not critical, so long as it is within about l/32th of aninch of its designed position. A reasonably correct location of the endnut is assured in the present tool by causing the side of the nut toabut upon the side 84 of opening 62 at the end of the left-hand movement(FIG. 15) of pawl 65. The exact location of the nut is achieved when thesevered nut passes downward over a guide surface 88 (FIG. 16), whichshifts the nut into a precisely located portion 89 of opening 62.Excessive movement of pawl 65 beyond this point is avoided by adjustingthe position of pivot block 68 in recess 69. The adjustment isaccomplished by appropriately turning a screw 85 connected to block 68and held against axial movement in housing 50.

It is understood that a recess 86 is formed in housing 50 ofa size andshape to accommodate the mechanisms used to effect the reciprocatingmovement of pawl 65, as well as to accommodate pawl 65 itself.

In the operation of the device of this invention, it is assumed thatmounting plate 44 is secured to the ram of punch press 39 to be movabletherewith and that housing 50 is secured to the bed or frame of press39, or to an appropriate fixture which is secured to such bed or frame.Where more than one application tool 40 is used in one press, a fixture(not shown) will be prepared to locate the workpiece relative to theapplication tools so that the nuts 20 are secured at the proper placeson the workpiece.

At the beginning ofa cycle, when the ram of the press is raised, theparts of the application tool will appear as in FIG. 10. It may be notedthat the bottom portion of drive link 73 has a forwardly extending leg73a the front vertical surface 87 of which is intended to serve as astop to limit the initial insertion of strip nuts 43 into the tool. Saidleg 73a is relatively narrow and, as seen in FIG. 14, operates in a slotin the side of opening 62 under punch 31 so that it is withdrawn as theworkpiece is advanced over said opening 62. Without leg 73a, it would bepossible to insert strip nuts into the tool to the extent that the endnut would be under punch 31 with the punch raised, and the subsequentdownward movement of the punch and the resulting movement of pawl 65 tothe left to advance a nut over opening 62 would cause the tool to jam,since the pawl could not move the strip nuts beyond the opening 62 overwhich the end nut is already located. Leg 73 a holds the strip nuts backuntil drive link 73 and pawl 65 move forward, so that the end nut movesforward with the link and pawl.

Thus, with tool 40 in the stage shown in FIG. 10, the strip nuts 43 areadvanced into contact with surface 87 by the operator of the press froma coil 38 located near the press, the workpiece is located under too] 40by an appropriate fixture (not shown) to receive a nut 20 at a desiredlocation thereon. and the punch press is then activated by the operatorto commence an application cycle. With the operation of the press, punch31 is lowered by the ram of the press against the resistance of spring54. The lowering of punch 31 causes roller 76 to ride along cam surface79 and thus move to the left as viewed in FIGS. 10 and 15. Drive link 73is caused to move to the left by roller 76 and, through rocker arm 66,imparts this movement, at an amplified rate to pawl 65. Said pawl 65drops into an opening 37 between adjacent nuts in the inserted stripnuts 43 and advances the strip nuts into the tool. Pawl 65 is so locatedrelative to surface 87 on leg 73a that it will be in an opening 37 atthe beginning of the movement of drive link 73. The position of pivotblock 68 is adjusted in a manner to insure such location of pawl 65.

As roller 76 leaves cam surface ,79 and thereafter rides on the verticalsurface 83 of punch 31, forward movement of the strip nuts ceases, andcontinued downward movement of punch 31 lowers punch 31 upon the end nut20 over opening 72, shears the said end nut from the strip nuts 43 atthe mid-point of the connecting flange parts 35, 36 and pushes the shankportion 19 of the severed nut against, and then through, workpiece 21until flanges 33, 34 abut against said workpiece, punching out arectangular slug from the workpiece in the process. The nut andworkpiece are then clinched together in the die 25 and the punch iswithdrawn by the upward movement of the ram of the press.

As punch 31 moves upward, pin 81 encounters cam surface 80 on the punch,and this causes said pin 81 to move to the right as viewed in FIG. 15.Roller'76 is free at this point to be moved in the same direction by camsurface 79. Drive link 73 thereforemoves to the right as viewed in FIG.15, taking pawl 65 with it through the operation of rocker arm 66. Stripnuts 43, however, are held against outward movement with pawl 65 byfinger spring 59 which has entered the space between adjacent nuts 20and blocks such outward movement. At the end of the upward movement ofpunch 31 the cycle is complete.

It may be observed that the specific forms of the nut and clinching dieare not material to this invention, although the nut will have aworkpiece-piercing shank portion and an abutment of some kind limitingthe movement of the shank portion through the workpiece, and that theapplication tool herein described and claimed may be used with equaleffectiveness with other types of clinch nuts. The tool is a unit whichmay be designed for a given size nut in strip form and treated fordesign purposes as a part of a standard system for applying clinch nutsto a workpiece. The nuts are supplied in the form of a coiled strip,along with the application tool 40 and bottom die, and the tool designerthen adapts the system to a particular fixture for handling the specificworkpiece to which the nuts are to be fastened. No apparatus forsingulating, orienting, transporting to a die and successively applyingloose nuts to a workpiece is required. Gang operation in a single punchpress of two or more application tools is entirely possible, therebyvastly simplifying, speeding up and cheapening the application of clinchnuts to a workpiece.

It is understood therefore that the foregoing description is merelyillustrative of a preferred embodiment of this invention, and that thescope of the invention is not to be limited thereto, but is to bedetermined by the appended claims.

I claim:

1. The method of effecting the attachment to a metal panel of piercenuts having two surfaces at the ends of shank portions and adjoined in acomposite strip which strip embodies a series of correspondinglyoriented and substantially discrete nuts joined together in alignedrelationship by connecting means having flexibility in a directionnormal to the top surfaces of the nuts, said method comprising the stepsof locating the panel over a die with the panel engaging a top surfaceof the die, advancing the end nut of the strip over the panel to apredetermined position over the die by engaging and moving a fixeddistance a transverse surface of the nut, the panel being disposedbetween the shank portion of said end nut and die and engaging anelevated supporting surface of the die which surrounds a substantiallycoplanar and continuous peripheral cutting edge of the die. severingsaid connecting means between said end nut and the rest of the strip,flexing a portion of the panel within said elevated supporting surfacetoward and into contact with said cutting edge by force applied to theshank portion of said nut and piercing said flexed portion of the panelwith the shank portion of the severed nut to cut a slug from the paneland effect the mounting of the nut on the panel, and securing the nut inits mounted position on the panel.

2. The method of effecting the attachment of a pierce nut to a metalpanel as defined in claim 1, and wherein the panel adjacent the nut isdeformed by the die as a result of force applied by the shank portion ofthe nut prior to piercing the panel.

3. The method according to claim 3, said step of advancing the end nutof the strip comprising engaging a transverse surface of the nutdisposed in the space between adjacent nuts.

4. The method according to claim 1, said step of advancing the end nutof the strip a fixed distance being performed independently of theposition of the leading edge of the nut.

UNIFIED STATES PATENT UFHCE QHHQATE @E CEUHUN Q PATENT N0w 3,877,133

DATED April 15 1975 ENVENTORB) William L. Grube if is certified thaterror appears in the above-identified patent and that said LettersPatent 9 are hereby corrected as shown below:

Col. 1, lines 66 and 67, delete entire sentence. Cole 3, line 18, after"nut" insert 20-; line 31, change "stip" to -strip. 0 Col 4. line 3change "puch" to punch.

Col 5, line 2, after "end" insert 82-- (201 8, line 18, delete "3 andinsert in its place l.

fir'gned and nineteenth Augusf1975 [seAL] Arrest:

RUTH c. MASON C. MARSHALL DAN-N 31110511 12 ffli" (mnmisslmu'r ufParenrsand Trademarks Gamma 4.

1. The method of effecting the attachment to a metal panel of piercenuts having two surfaces at the ends of shank portions and adjoined in acomposite strip which strip embodies a series of correspondinglyoriented and substantially discrete nuts joined together in alignedrelationship by connecting means having flexibility in a directionnormal to the top surfaces of the nuts, said method comprising the stepsof locating the panel over a die with the panel engaging a top surfaceof the die, advancing the end nut of the strip over the panel to apredetermined position over the die by engaging and moving a fixeddistance a transverse surface of the nut, the panel being disposedbetween the shank portion of said end nut and die and engaging anelevated supporting surface of the die which surrounds a substantiallycoplanar and continuous peripheral cutting edge of the die, severingsaid conNecting means between said end nut and the rest of the strip,flexing a portion of the panel within said elevated supporting surfacetoward and into contact with said cutting edge by force applied to theshank portion of said nut and piercing said flexed portion of the panelwith the shank portion of the severed nut to cut a slug from the paneland effect the mounting of the nut on the panel, and securing the nut inits mounted position on the panel.
 2. The method of effecting theattachment of a pierce nut to a metal panel as defined in claim 1, andwherein the panel adjacent the nut is deformed by the die as a result offorce applied by the shank portion of the nut prior to piercing thepanel.
 3. The method according to claim 3, said step of advancing theend nut of the strip comprising engaging a transverse surface of the nutdisposed in the space between adjacent nuts.
 4. The method according toclaim 1, said step of advancing the end nut of the strip a fixeddistance being performed independently of the position of the leadingedge of the nut.